Clinical Investigations Respiration 2014;87:372–378 DOI: 10.1159/000358442
Received: August 19, 2013 Accepted after revision: December 24, 2013 Published online: April 4, 2014
The Prevalence of and Risk Factors for Sleep-Disordered Breathing in an Elderly Korean Population Sang Don Lee Suk-Hoon Kang Gawon Ju Ji Won Han Tae Hui Kim Chung Suk Lee Tae Kim Ki Woong Kim In-Young Yoon Department of Neuropsychiatry, Seoul National University Bundang Hospital, Seongnam, Republic of Korea
Key Words Apnea/hypopnea index · Body mass index · Elderly · Polysomnography · Sleep-disordered breathing · Snoring
Abstract Background: There are just a few epidemiological studies on sleep-disordered breathing (SDB) in the elderly, and the results are inconsistent. Study Objectives: We sought to investigate the prevalence of and risk factors for SDB in a representative elderly population with the use of attended nocturnal polysomnography (NPSG). Methods: Among 6,959 individuals aged ≥60 years living in Yongin City, Korea, 696 subjects were selected using random sampling. All the subjects were invited to visit a hospital for NPSG, and SDB was defined as an apnea-hypopnea index ≥15. Results: Of the 696 participants investigated, 348 participants completed the sleep study and clinical evaluation. SDB was observed in 127 of the 348 participants, and the prevalence of SDB was 36.5% (52.6% in males and 26.3% in females). A body mass index ≥25 was associated with SDB in both male and female subjects, particularly in males, whereas snoring was independently associated with SDB in female participants only. In male participants, SDB was a significant risk factor for hypertension (p = 0.025). Conclusions: SDB was
© 2014 S. Karger AG, Basel 0025–7931/14/0875–0372$39.50/0 E-Mail [email protected] www.karger.com/res
found to be common among elderly Koreans, and it was more prevalent and severe in male than in female subjects. Health consequences of SDB in the elderly need to be further explored. © 2014 S. Karger AG, Basel
Introduction
Sleep-disordered breathing (SDB) is a common sleep disorder [1, 2] associated with significant health problems of the cardiovascular system, cognitive function and daytime alertness [3–8]. SDB is frequently observed with aging and can result in unwanted effects on the well-being of the elderly; however, only a few studies have been carried out on the prevalence of SDB in the elderly and its risk factors, and their results are inconsistent. In the middle-aged population, SDB was defined as an apnea-hypopnea index (AHI) ≥5 and daytime sleepiness, and prevalence was around 4% in men and 2–3% in women [1, 9, 10]. Obesity, male gender, snoring and alcohol consumption have been identified as risk factors for SDB in middle-aged subjects [11–13]. On the other hand, the prevalence of SDB in the elderly, defined as AHI ≥15 or 20, ranged from 13.3 to 57% [13–16], and controversies reIn-Young Yoon, MD, PhD Department of Neuropsychiatry Seoul National University Bundang Hospital 166 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-707 (Republic of Korea) E-Mail iyoon @ snu.ac.kr
garding risk factors for SDB in the elderly, such as body weight, male gender and snoring, still remain. Previous studies on the prevalence of SDB in the elderly have several limitations. Although they were the first to report the prevalence of SDB in a representative sample of elderly subjects, Ancoli-Israel et al. [14] did not measure oxygen saturation and determine arousals, but evaluated respiratory events only from airflow. In other studies with a two-stage design, a small proportion of the original samples participated in the second stage of the study [15, 17– 19]. Young et al. [13] reported that snoring and witnessed apnea were not useful for screening SDB in the elderly, and so selecting subjects on the basis of snoring might not be appropriate for the elderly population. Using home-based polysomnography (PSG) was another limitation in the evaluation of SDB [13, 16], as there are some discrepancies between AHI determined by home-based and attended laboratory PSG, particularly in severe SDB [20, 21]. Thus, we need to perform a prevalence study on SDB in the elderly overcoming the limitations of previous studies. The purpose of this study was to investigate the prevalence of SDB and its related factors in the elderly Korean population. For this purpose, elderly people randomly selected from the community were evaluated during attended full-night PSG in a one-stage design.
Materials and Methods Study Subjects This study was part of the Korean Longitudinal Study on Cognitive Aging and Dementia, a population-based prospective cohort study of cognitive function with aging and dementia in the Korean elderly population aged ≥60 years. We conducted the study from January 2010 to February 2011 on old adults living in Jukjeon-dong, a district of Yongin City, Korea. Among the 6,959 residents of Jukjeon-dong aged ≥60 years, 10% (n = 696) were randomly selected based on the residential roster. As we expected the prevalence of elderly SDB to be 30–40% in the Korean elderly population, the calculated sample size was 323–369 at the precision of 0.05 [22]. Thus, the sample size of 696 with the expected response rate of 50–60% could represent the elderly Korean population. All the subjects were invited to visit the Seoul National University Bundang Hospital for clinical evaluation and nocturnal PSG (NPSG). This study was approved by our institutional review board, and all subjects who had clinical evaluations provided written informed consent themselves or via their legal guardians. Clinical Evaluation Anthropometric evaluation included height, weight, and neck, waist and hip circumferences. Snoring and witnessed apnea events were assessed by the STOP questionnaire [23], which includes the following two questions: ‘Do you snore loudly (louder than talking or loud enough to be heard through closed doors)?’ and ‘Has any-
Sleep-Disordered Breathing in the Elderly
one observed you stop breathing during your sleep?’ Subjects who answered ‘yes’ to each question were regarded positive for snoring or witnessed apnea. The Pittsburgh sleep quality index (PSQI) was used to measure subjective sleep complaints, and the Epworth Sleepiness Scale (ESS) was applied to assess daytime sleepiness, which was defined as ESS score >10. Diabetes mellitus was defined as fasting blood glucose >126 mg/dl and hypertension was defined as systolic blood pressure >140 mm Hg or diastolic blood pressure >90 mm Hg or both, or current use of antihypertensive drugs. Cardiac diseases other than hypertension included coronary artery disease, angina pectoris, congestive heart failure, cardiac tumors and other cardiac diseases. After clinical evaluation, subjects were recommended to participate in NPSG on another day. Nocturnal Polysomnography One night of attended PSG was done. We used EmblaTM N7000 (Embla, Reykjavik, Iceland). Electroencephalography electrodes were placed at C4/A1, C3/A2, O1/A2 and O2/A1, and two electrooculography electrodes were applied at the sides of both eyes to record horizontal and vertical eye movements. Electromyography electrodes were positioned at the submentalis muscles and both anterior tibialis muscles. Strain gauges were used for recording chest and abdominal respiratory movements, and nasal pressure cannulas were employed to record airflow. Oxygen saturation was measured using a pulse oximeter applied to the index finger. Based on the criteria of Rechtschaffen and Kales [24], sleep was scored at every 30-second epoch of the NPSG. Apnea was defined as complete cessation of airflow for at least 10 s. It was further divided into obstructive, central and mixed apnea. Hypopnea was defined as a clear decrease in airflow (>50%) for at least 10 s or a discernible reduction in airflow for at least 10 s associated with electroencephalographic arousal or oxygen desaturation (≥4%) [25]. The AHI was defined as the total number of apneas and hypopneas per hour of sleep, and the oxygen desaturation index was calculated as the number of oxygen desaturations (≥4%) per hour of sleep. The criterion for SDB was AHI ≥15, and data for three AHI cutoff values (5, 15, and 30) are presented. Statistical Analysis Prevalence rates were calculated by gender (men/women) and age (60–64/65–69/75–89 years) strata. Standardized prevalence rates of older Koreans were estimated using a direct standardization method in which the prevalence rates were adjusted by age and gender to the total Korean population based on the 2011 national census. Comparison between groups was done with the independent t tests for continuous variables and Pearson’s χ2 test for discrete variables. Multiple logistic regression analysis for SDB was employed with gender, age, body mass index (BMI) and snoring being predictors. All significance tests were two sided, and p < 0.05 was considered statistically significant. All analyses were done with SPSS version 18.0 for Windows (SPSS Inc., Chicago, Ill., USA).
Results
Of the 696 subjects, 466 participated in the clinical evaluation and 354 of them underwent NPSG. Of the 354 participants, 6 subjects were excluded from analysis beRespiration 2014;87:372–378 DOI: 10.1159/000358442
373
cause of insufficient sleep time (total sleep time
Received: August 19, 2013 Accepted after revision: December 24, 2013 Published online: April 4, 2014
The Prevalence of and Risk Factors for Sleep-Disordered Breathing in an Elderly Korean Population Sang Don Lee Suk-Hoon Kang Gawon Ju Ji Won Han Tae Hui Kim Chung Suk Lee Tae Kim Ki Woong Kim In-Young Yoon Department of Neuropsychiatry, Seoul National University Bundang Hospital, Seongnam, Republic of Korea
Key Words Apnea/hypopnea index · Body mass index · Elderly · Polysomnography · Sleep-disordered breathing · Snoring
Abstract Background: There are just a few epidemiological studies on sleep-disordered breathing (SDB) in the elderly, and the results are inconsistent. Study Objectives: We sought to investigate the prevalence of and risk factors for SDB in a representative elderly population with the use of attended nocturnal polysomnography (NPSG). Methods: Among 6,959 individuals aged ≥60 years living in Yongin City, Korea, 696 subjects were selected using random sampling. All the subjects were invited to visit a hospital for NPSG, and SDB was defined as an apnea-hypopnea index ≥15. Results: Of the 696 participants investigated, 348 participants completed the sleep study and clinical evaluation. SDB was observed in 127 of the 348 participants, and the prevalence of SDB was 36.5% (52.6% in males and 26.3% in females). A body mass index ≥25 was associated with SDB in both male and female subjects, particularly in males, whereas snoring was independently associated with SDB in female participants only. In male participants, SDB was a significant risk factor for hypertension (p = 0.025). Conclusions: SDB was
© 2014 S. Karger AG, Basel 0025–7931/14/0875–0372$39.50/0 E-Mail [email protected] www.karger.com/res
found to be common among elderly Koreans, and it was more prevalent and severe in male than in female subjects. Health consequences of SDB in the elderly need to be further explored. © 2014 S. Karger AG, Basel
Introduction
Sleep-disordered breathing (SDB) is a common sleep disorder [1, 2] associated with significant health problems of the cardiovascular system, cognitive function and daytime alertness [3–8]. SDB is frequently observed with aging and can result in unwanted effects on the well-being of the elderly; however, only a few studies have been carried out on the prevalence of SDB in the elderly and its risk factors, and their results are inconsistent. In the middle-aged population, SDB was defined as an apnea-hypopnea index (AHI) ≥5 and daytime sleepiness, and prevalence was around 4% in men and 2–3% in women [1, 9, 10]. Obesity, male gender, snoring and alcohol consumption have been identified as risk factors for SDB in middle-aged subjects [11–13]. On the other hand, the prevalence of SDB in the elderly, defined as AHI ≥15 or 20, ranged from 13.3 to 57% [13–16], and controversies reIn-Young Yoon, MD, PhD Department of Neuropsychiatry Seoul National University Bundang Hospital 166 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 463-707 (Republic of Korea) E-Mail iyoon @ snu.ac.kr
garding risk factors for SDB in the elderly, such as body weight, male gender and snoring, still remain. Previous studies on the prevalence of SDB in the elderly have several limitations. Although they were the first to report the prevalence of SDB in a representative sample of elderly subjects, Ancoli-Israel et al. [14] did not measure oxygen saturation and determine arousals, but evaluated respiratory events only from airflow. In other studies with a two-stage design, a small proportion of the original samples participated in the second stage of the study [15, 17– 19]. Young et al. [13] reported that snoring and witnessed apnea were not useful for screening SDB in the elderly, and so selecting subjects on the basis of snoring might not be appropriate for the elderly population. Using home-based polysomnography (PSG) was another limitation in the evaluation of SDB [13, 16], as there are some discrepancies between AHI determined by home-based and attended laboratory PSG, particularly in severe SDB [20, 21]. Thus, we need to perform a prevalence study on SDB in the elderly overcoming the limitations of previous studies. The purpose of this study was to investigate the prevalence of SDB and its related factors in the elderly Korean population. For this purpose, elderly people randomly selected from the community were evaluated during attended full-night PSG in a one-stage design.
Materials and Methods Study Subjects This study was part of the Korean Longitudinal Study on Cognitive Aging and Dementia, a population-based prospective cohort study of cognitive function with aging and dementia in the Korean elderly population aged ≥60 years. We conducted the study from January 2010 to February 2011 on old adults living in Jukjeon-dong, a district of Yongin City, Korea. Among the 6,959 residents of Jukjeon-dong aged ≥60 years, 10% (n = 696) were randomly selected based on the residential roster. As we expected the prevalence of elderly SDB to be 30–40% in the Korean elderly population, the calculated sample size was 323–369 at the precision of 0.05 [22]. Thus, the sample size of 696 with the expected response rate of 50–60% could represent the elderly Korean population. All the subjects were invited to visit the Seoul National University Bundang Hospital for clinical evaluation and nocturnal PSG (NPSG). This study was approved by our institutional review board, and all subjects who had clinical evaluations provided written informed consent themselves or via their legal guardians. Clinical Evaluation Anthropometric evaluation included height, weight, and neck, waist and hip circumferences. Snoring and witnessed apnea events were assessed by the STOP questionnaire [23], which includes the following two questions: ‘Do you snore loudly (louder than talking or loud enough to be heard through closed doors)?’ and ‘Has any-
Sleep-Disordered Breathing in the Elderly
one observed you stop breathing during your sleep?’ Subjects who answered ‘yes’ to each question were regarded positive for snoring or witnessed apnea. The Pittsburgh sleep quality index (PSQI) was used to measure subjective sleep complaints, and the Epworth Sleepiness Scale (ESS) was applied to assess daytime sleepiness, which was defined as ESS score >10. Diabetes mellitus was defined as fasting blood glucose >126 mg/dl and hypertension was defined as systolic blood pressure >140 mm Hg or diastolic blood pressure >90 mm Hg or both, or current use of antihypertensive drugs. Cardiac diseases other than hypertension included coronary artery disease, angina pectoris, congestive heart failure, cardiac tumors and other cardiac diseases. After clinical evaluation, subjects were recommended to participate in NPSG on another day. Nocturnal Polysomnography One night of attended PSG was done. We used EmblaTM N7000 (Embla, Reykjavik, Iceland). Electroencephalography electrodes were placed at C4/A1, C3/A2, O1/A2 and O2/A1, and two electrooculography electrodes were applied at the sides of both eyes to record horizontal and vertical eye movements. Electromyography electrodes were positioned at the submentalis muscles and both anterior tibialis muscles. Strain gauges were used for recording chest and abdominal respiratory movements, and nasal pressure cannulas were employed to record airflow. Oxygen saturation was measured using a pulse oximeter applied to the index finger. Based on the criteria of Rechtschaffen and Kales [24], sleep was scored at every 30-second epoch of the NPSG. Apnea was defined as complete cessation of airflow for at least 10 s. It was further divided into obstructive, central and mixed apnea. Hypopnea was defined as a clear decrease in airflow (>50%) for at least 10 s or a discernible reduction in airflow for at least 10 s associated with electroencephalographic arousal or oxygen desaturation (≥4%) [25]. The AHI was defined as the total number of apneas and hypopneas per hour of sleep, and the oxygen desaturation index was calculated as the number of oxygen desaturations (≥4%) per hour of sleep. The criterion for SDB was AHI ≥15, and data for three AHI cutoff values (5, 15, and 30) are presented. Statistical Analysis Prevalence rates were calculated by gender (men/women) and age (60–64/65–69/75–89 years) strata. Standardized prevalence rates of older Koreans were estimated using a direct standardization method in which the prevalence rates were adjusted by age and gender to the total Korean population based on the 2011 national census. Comparison between groups was done with the independent t tests for continuous variables and Pearson’s χ2 test for discrete variables. Multiple logistic regression analysis for SDB was employed with gender, age, body mass index (BMI) and snoring being predictors. All significance tests were two sided, and p < 0.05 was considered statistically significant. All analyses were done with SPSS version 18.0 for Windows (SPSS Inc., Chicago, Ill., USA).
Results
Of the 696 subjects, 466 participated in the clinical evaluation and 354 of them underwent NPSG. Of the 354 participants, 6 subjects were excluded from analysis beRespiration 2014;87:372–378 DOI: 10.1159/000358442
373
cause of insufficient sleep time (total sleep time
